dart-base-x

Inspired by base-x.

Fast base encoding / decoding of any given alphabet using bitcoin style leading zero compression.

WARNING: This module is NOT RFC3548 compliant, it cannot be used for base16 (hex), base32, or base64 encoding in a standards compliant manner.

Install

dart pub add dart_base_x

Example

Base58

import 'dart:typed_data';

import 'package:dart_base_x/dart_base_x.dart';

void main() {
  String base58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';

  BaseXCodec bs58 = BaseXCodec(base58);

  Uint8List decoded =
      bs58.decode('5Kd3NBUAdUnhyzenEwVLy9pBKxSwXvE9FMPyR4UKZvpe6E3AgLr');

  print(decoded);
  // => [128, 237, 219, 220, 17, 104, 241, 218, 234, 219, 211, 228, 76, 30, 63, 143, 90, 40, 76, 32, 41, 247, 138, 210, 106, 249, 133, 131, 164, 153, 222, 91, 25, 19, 164, 248, 99]

  print(bs58.encode(decoded));
  // => 5Kd3NBUAdUnhyzenEwVLy9pBKxSwXvE9FMPyR4UKZvpe6E3AgLr
}

Alphabets

See below for a list of commonly recognized alphabets, and their respective base.

BaseAlphabet
201
801234567
110123456789a
160123456789abcdef
320123456789ABCDEFGHJKMNPQRSTVWXYZ
32ybndrfg8ejkmcpqxot1uwisza345h769 (z-base-32)
360123456789abcdefghijklmnopqrstuvwxyz
58123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz
620123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ
64ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
67ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.!~

How it works

It encodes octet arrays by doing long divisions on all significant digits in the array, creating a representation of that number in the new base. Then for every leading zero in the input (not significant as a number) it will encode as a single leader character. This is the first in the alphabet and will decode as 8 bits. The other characters depend upon the base. For example, a base58 alphabet packs roughly 5.858 bits per character.

This means the encoded string 000f (using a base16, 0-f alphabet) will actually decode to 4 bytes unlike a canonical hex encoding which uniformly packs 4 bits into each character.

While unusual, this does mean that no padding is required and it works for bases like 43.

LICENSE MIT

A direct derivation of the base58 implementation from bitcoin/bitcoin , generalized for variable length alphabets.

Libraries

dart_base_x
Support for doing something awesome.